This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2001-43799, filed on Feb. 20, 2001; the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a display unit and a manufacturing method thereof, and more particularly to an antireflection antistatic film formed on a face surface of a Braun tube.
2. Description of the Related Art
It is possible to cause a surface treatment film of a display device to have an antireflection antistatic function, a function of lowering transmittance of a face surface of the display unit and improving contrast of a picture, and so forth. Furthermore, by causing the surface treatment film to have a wavelength selective absorption characteristic, color purity of luminous color can be improved. Moreover, it is also possible to cause a Braun tube to have not only the antistatic function but also an electromagnetic shield function.
In view of the above, a two-layered antireflection antistatic film composed of a conductive layer made of metal minute particles and a protect layer made of SiO2 has recently been utilized. For this conductive layer, at least one kind of metal minute particles or metal compound minute particles selected from metals belonging to 3A, 4A, 5A, 6A, 7A, 8, 1B, 2B, 3B, 4B, and 5B groups is used. Especially when metal minute particles, for example, an Agxe2x80x94Pd alloy, an Auxe2x80x94Pd alloy, and so on, which themselves have a light absorption characteristic, are used, the surface treatment film can have the function of lowering the transmittance of the surface treatment film and improving contrast of a picture.
In manufacturing this two-layered antireflection antistatic film, it is necessary to take productivity such as treating time required for film formation and plant investment into consideration. From the viewpoint of such productivity, a wet method is often used in manufacturing the two-layered antireflection antistatic film. As this wet method, for example, a spin-coating method, a dipping method, and so forth can be named.
The spin-coating method is a method of forming a film by dispersing a solution uniformly over a surface through the use of a centrifugal force resulting from the rotation of the surface. The dipping method is a method of forming a film uniformly through the use of dispersion due to self-weight of a solution onto the surface.
However, the decrease in the transmittance of the conductive layer in order to improve the contrast of a picture causes noticeable uneven coating of the conductive layer and is likely to cause deterioration in picture quality. A multi-layered structure in which an absorption layer including organic coloring matter and so on is provided in addition to the conductive layer made of the metal minute particles is an effective solution to such problem.
In general, drying at a relatively low temperature and for a short treating time is preferable for the film formation from the viewpoint of productivity. Such drying condition for the film formation is preferably, for example, a temperature of approximately 20xc2x0 C. to 35xc2x0 C. and approximately one to five minute treating time.
However, when the multi-layered antireflection antistatic film having the aforesaid absorption layer is to be formed under the preferable condition determined from the viewpoint of high productivity, such as the relatively low temperature and short treating time as described above, substances constituting the conductive layer sink into the absorption layer, which is likely to cause the deterioration in the picture quality. Therefore, it is necessary to laminate each of the layers while drying each of them by forced heating (for example, at a temperature of 50xc2x0 C. to 100xc2x0 C. for three to ten minutes) using a heat source such as a warm air, a heater, or the like.
The inventors of the present invention conducted experiments to examine influences of such film formation condition. First, the absorption layer was dried at a temperature of 30xc2x0 C. for five minutes after coating by the spin-coating method. Next, the conductive layer and the protect layer were formed in sequence under the similar condition. In this case, a solvent and the metal minute particles included in a conductive layer forming solution sink into the absorption layer to cause deterioration in a conduction characteristic and an antireflection characteristic and further cause a large extent of impairment not only in desired transmittance but also in a function required for the surface treatment film of the display unit.
Meanwhile, the layers were laminated in sequence with the drying condition being changed to a temperature of 60xc2x0 C. and five minute treating time to form the multi-layered antireflection antistatic film. In this case, no impairment in functions such as the conduction characteristic, the antireflection characteristic, and so forth was caused and a desired value was obtained for the film transmittance and so on.
As described above,the increase in the drying temperature prevents deterioration in the conduction characteristic and the antireflection characteristic and enables the film transmittance to be the desired value. However, when the drying is performed at a higher temperature than a normal temperature as described above, a heating device or a cooling device for the face surface is necessary, which results in increase in facility cost. Meanwhile, the drying at a low temperature needs lengthened treating time to lower productivity.
Therefore, it is an object of the present invention to provide a display unit which has a multi-layered antireflection antistatic film free from external appearance abnormality and superior in a contrast characteristic of a displayed picture. It is another object of the present invention to provide a manufacturing method of a display unit free from external appearance abnormality and superior in a contrast characteristic, under the condition of a relatively low temperature and short treating time without using a large-scaled heating device and cooling device.
The display unit of the present invention includes a face surface and a multi-layered antireflection antistatic film composed of three layers or more which are formed on the face surface. The multi-layered antireflection antistatic film has an absorption layer, a conductive layer, and a protect layer in the order from a face surface side, and the absorption layer includes at least one kind of organic coloring matter, SiO2, and a silane coupling agent, in which the silane coupling agent content is seven times or less by weight the total content of SiO2 and the organic coloring matter.
In the display device of the present invention having the absorption layer, the conductive layer, and the protect layer, the absorption layer includes at least one kind of the organic coloring matter, SiO2, and the silane coupling agent to enable the display device to be free from external appearance abnormality, superior in a contrast characteristic, and superior in productivity.
As the silane coupling agent included in the absorption layer, it is effective to use an agent having at least one functional group selected from, for example, an alkyl group, a vinyl group, a phenyl group, an epoxy group, a carbonyl group, an ether group, a carboxyl group, an ester group, a mercapt group, an amido group, an amino group, a cyano group, and a nitro group.
The organic coloring matter included in the absorption layer preferably has a selective absorption characteristic in a range of 400 nm to 750 nm.
The conductive layer preferably includes metal minute particles or metal compound minute particles including at least one kind of element selected from 3A, 4A, 5A, 6A, 7A, 8, 1B, 2B, 3B, 4B, and 5B groups.
It is preferable that the film transmittance of the absorption layer in the range of 400 nm to 750 nm is 90% to 50%, the film transmittance of the conductive layer in a range of 400 nm to 750 nm is 100% to 70%, and the film transmittance as a multi-layered film is 90% to 40%.
The luminous reflectance of the multi-layered antireflection antistatic film in a range of 400 nm to 750 nm is preferably 2.0% or lower and its surface resistivity is preferably 500 kxcexa9/square or lower.
The display unit of the present invention is used suitably, for example, as a Braun tube.